JP3847506B2 - Zoom lens - Google Patents

Description

ただし、ｒは近軸曲率半径、Ｋは円錐係数、A₄、A₆、A₈、A₁₀ はそれぞれ４次、６次、８次、１０次の非球面係数である。
【００６３】

【００６４】

【００６５】

【００６６】

【００６７】
上記実施例１〜４の無限遠合焦時の収差図をそれぞれ図５〜図８に示す。各収差図中、（ａ）は広角端での収差、（ｂ）は中間焦点距離での収差、（ｃ）は望遠端での収差である。これら図中、ＳＡは球面収差、ＡＳは非点収差、ＤＴは歪曲収差、ＣＣは倍率色収差である。なお、ＦＩＹは像高である。
【００６８】
次に、上記実施例１〜４の前記条件式（１）〜（１８）に関するパラメータの値を下記の表に示す。
【００６９】

【００７０】
また、上記実施例１〜４のその他の条件式に関する値を次に示す。
実施例１
Δ_L5／Δ_L4 １．００４
Ｄ₄₅／ｆ₅ ０．０８３８
（Ｒ₅₁＋Ｒ₅₂）／（Ｒ₅₁−Ｒ₅₂） −０．３４６
ｆ₁ ／ｆ_W −２．８９
Ｒ₄ ／ｆ_W ２．３４２
Ｈｂ_1abs／ｆ_1abs ０．２７８
Ｈｂ_1abs／（ｆ_1abs・ｆ₂ ） ０．０１０７
変倍比 ３．０
広角端画角２ω ７６．３°
実施例２
Δ_L5／Δ_L4 ０．９９１
Ｄ₄₅／ｆ₅ ０．０８８７
（Ｒ₅₁＋Ｒ₅₂）／（Ｒ₅₁−Ｒ₅₂） −０．５５６
ｆ₁ ／ｆ_W −２．７５５
Ｒ₄ ／ｆ_W ２．２４３
Ｈｂ_1abs／ｆ_1abs ０．２８３
Ｈｂ_1abs／（ｆ_1abs・ｆ₂ ） ０．０１１８
変倍比 ３．０
広角端画角２ω ７６．３°
実施例３
Δ_L5／Δ_L4 ０．９８７
Ｄ₄₅／ｆ₅ ０．０８７３
（Ｒ₅₁＋Ｒ₅₂）／（Ｒ₅₁−Ｒ₅₂） −１．０７６
ｆ₁ ／ｆ_W −１．８６４
Ｒ₄ ／ｆ_W １．８３９
Ｄ₆ ／ｆ_W ０．８５７
Ｈｂ_1abs／ｆ_1abs ０．６８３
Ｈｂ_1abs／（ｆ_1abs・ｆ₂ ） ０．０３８０
ｆ₃₁／ｆ₃₂ ０．７３８
変倍比 ３．０
広角端画角２ω ７６．３°
実施例４
ｆ₁ ／ｆ_W −２．２３５
Ｒ₂ ／ｆ_W ２．０２４
Ｈｂ_1abs／ｆ_1abs ０．５２０
Ｈｂ_1abs／（ｆ_1abs・ｆ₂ ） ０．０２７９
ｆ₃₁／ｆ₃₂ ０．３２７
変倍比 ３．０
広角端画角２ω ７６．３° 。
【００７１】
以上のような本発明の大口径広角ズームレンズは、例えば図９に示すような電子カメラ１１の撮影用対物光学系１２に用いることができる。図９中、（ａ）は前側から見た電子カメラ１１の斜視図、（ｂ）は後側から見た電子カメラ１１の斜視図、（ｃ）は電子カメラ１１の光学系を示す光路図であり、電子カメラ１１は、撮影用光路を有する撮影光学系１２、撮影光学系１２の光路中に配され、ファインダー用光路を分離させるハーフミラープリズム１３、ハーフミラープリズム１３により形成されたファインダー用の像を正立正像させるダハ反射面を有するペンタプリズム１４、接眼レンズ１５、レリーズボタン１６、ストロボ１７、液晶表示モニタ１８、ＣＣＤ１９、ＣＣＤ１９に入射した像を電気信号に変換するコントローラ２０、撮像した像を電気的に記録する記録媒体（例えば、ＰＣカード）に記録するデータ書き込み装置２１等を含んでいる。
【００７２】
また、撮影光学系１２の光路では、ハーフミラープリズム１３のＣＣＤ１９側にローパスフィルター２２とＩＲカットフィルター２３を配してある。
【００７３】
また、本発明の大口径広角ズームレンズは、例えば図１０に示すようなビデオカメラ２４（概念図）の撮影用対物光学系１２に用いることができる。図１０はビデオカメラ２４の光学系を示す光路図であり、ビデオカメラ２４は、撮影用光路を有する撮影光学系１２、撮影光学系１２による像を撮像するＣＣＤ１９、ＣＣＤ１９により撮像された像を表示するＬＣＤ（液晶表示素子）２５、ＬＣＤ２５からの像を観察者眼球へと導く接眼レンズ１５、撮影のＯＮ／ＯＦＦ切換えスイッチ２６、録音マイク２７、液晶表示モニタ１８、ＣＣＤ１９に入射した像を電気信号に変換するコントローラ２０、撮像した像を電気的に記録する記録媒体（例えば、磁気テープ、デジタルビデオテープ、ＤＶＤ）に記録可能なデータ書き込み装置２１等を含んでいる。
【００７４】
また、撮影光学系１２の光路中にローパスフィルター２２とＩＲカットフィルター２３を配してある。
【００７５】
以上の本発明のズームレンズは、例えば次のように構成することができる。
【００７６】
〔１〕 物体側から順に、負の屈折力を有する第１群、正の屈折力を有する第２群、負の屈折力を有する第３群、正の屈折力を有する第４群、正の屈折力を有する第５群よりなり、物点移動の際の合焦は第５群で行うことを特徴とするズームレンズ。
【００７７】
〔２〕 物体側から順に、負の屈折力を有する第１群、正の屈折力を有する第２群、負の屈折力を有する第３群、正の屈折力を有する第４群、正の屈折力を有する第５群よりなり、広角端より望遠端への変倍を、第１群と第２群の間隔及び第３群と第４群の間隔は減少し、第２群と第３群の間隔及び第４群と結像面の間隔は増大し、物点移動の際の合焦は第５群で行うことを特徴とするズームレンズ。
【００７８】
〔３〕 物体側から順に、負の屈折力を有する第１群、正の屈折力を有する第２群、負の屈折力を有する第３群、正の屈折力を有する第４群、正の屈折力を有する第５群よりなり、広角端より望遠端への変倍を、第１群と第２群の間隔及び第３群と第４群の間隔は減少し、第２群と第３群の間隔及び第４群と結像面の間隔は増大し、物点移動の際の合焦は第５群で行い、その際、近距離から無限遠方向にフォーカシングさせる場合には、第５群を像側に移動し、無限遠方向から近距離方向にフォーカシングさせる場合には第５群を物体側に移動することを特徴とするズームレンズ。
【００７９】
〔４〕 物体側から順に、負の屈折力を有する第１群、正の屈折力を有する第２群、負の屈折力を有する第３群、正の屈折力を有する第４群、正の屈折力を有する第５群よりなり、広角端より望遠端への変倍を、第１群と第２群の間隔及び第３群と第４群及び第３群と第５群の間隔は減少し、第２群と第３群の間隔及び第４群と結像面及び第５群と結像面の間隔は増大し、第５群を移動させることにより被写体へのフォーカシングを行うことを特徴とするズームレンズ。
【００８０】
〔５〕 物体側から順に、負の屈折力を有する第１群、正の屈折力を有する第２群、負の屈折力を有する第３群、正の屈折力を有する第４群、正の屈折力を有する第５群よりなり、物点移動の際の合焦は第５群で行う光学系において、以下の条件を満足することを特徴とするズームレンズ。
【００８１】
（１） −０．２＜β_V ＜０．８
（２） ０．６＜Δ_L5／Δ_L4＜１．２
（３） ０．０５＜Ｄ₄₅／ｆ₅ ＜０．１５
ただし、β_V は広角端無限物点合焦時の第５群の倍率、Δ_L4は第４群の無限物点合焦状態での広角端から望遠端にかけての移動量、Δ_L5は第５群の無限物点合焦状態での広角端から望遠端にかけての移動量、Ｄ₄₅は望遠端無限遠物点合焦時における第４群と第５群との光軸上空気間隔、ｆ₅ 第５群の焦点距離である。
【００８２】
〔６〕 前記第５群が非球面を含む正の単レンズ成分又は接合された正のレンズ成分からなることを特徴とする上記１から５の何れか１項記載のズームレンズ。
【００８３】
〔７〕 前記第５群が正レンズ成分を含み、該正レンズ成分のシェープファクターが以下の条件を満足することを特徴とする上記１から６の何れか１項記載のズームレンズ。
【００８４】
（４） −２＜（Ｒ₅₁＋Ｒ₅₂）／（Ｒ₅₁−Ｒ₅₂）＜０．２
ただし、Ｒ₅₁は第５群の最も物体側の面の曲率半径、Ｒ₅₂は第５群の最も像側の面の曲率半径である。
【００８５】
〔８〕 物体側から順に、少なくとも負の屈折力を有する第１群、正の屈折力を有する第２群、負の屈折力を有する第３群、正の屈折力を有する第４群を含み、前記第１群が物体側から順に、正レンズ、負メニスカスレンズ、負レンズと正メニスカスレンズの接合からなる負レンズ成分よりなり、以下の条件を満足することを特徴とするズームレンズ。
【００８６】
（５） −４．０＜ｆ₁ ／ｆ_W ＜−１．５
（６） １．５５＜ｎ₁ ＜１．８
（７） １．３＜Ｒ₄ ／ｆ_W ＜３．５
（８） ３７＜ν₁ ＜８３
ただし、ｆ₁ は第１群の焦点距離、ｆ_W は全系の広角端での焦点距離、ｎ₁ は第１群の最も物体側の正レンズの媒質屈折率、Ｒ₄ は第１群の負メニスカスレンズの凹面の曲率半径、ν₁ は第１群の最も物体側の正レンズの媒質アッベ数である。
【００８７】
〔９〕 物体側から順に、少なくとも負の屈折力を有する第１群、正の屈折力を有する第２群、負の屈折力を有する第３群、正の屈折力を有する第４群を含み、前記第１群が物体側から順に、正レンズ、負メニスカスレンズ、負レンズ、正メニスカスレンズよりなり、以下の条件を満足することを特徴とするズームレンズ。
【００８８】
（９） ０．５＜Ｄ₆ ／ｆ_W ＜１．２
（10） −４．０＜ｆ₁ ／ｆ_W ＜−１．５
（11） １．５５＜ｎ₁ ＜１．８
（12） １．３＜Ｒ₄ ／ｆ_W ＜３．５
（13） ３７＜ν₁ ＜８３
ただし、Ｄ₆ は第１群の負レンズと正メニスカスレンズとの間隔、ｆ₁ は第１群の焦点距離、ｆ_W は全系の広角端での焦点距離、ｎ₁ は第１群の最も物体側の正レンズの媒質屈折率、Ｒ₄ は第１群の負メニスカスレンズの凹面の曲率半径、ν₁ は第１群の最も物体側の正レンズの媒質アッベ数である。
【００８９】
〔１０〕 物体側から順に、少なくとも負の屈折力を有する第１群、正の屈折力を有する第２群、負の屈折力を有する第３群、正の屈折力を有する第４群を含み、前記第１群が物体側から順に、負メニスカスレンズ、負レンズ、正レンズと負レンズとの接合からなる正メニスカスレンズ成分よりなり、以下の条件を満足することを特徴とするズームレンズ。
【００９０】
（14） −４．０＜ｆ₁ ／ｆ_W ＜−１．５
（15） １．３＜Ｒ₂ ／ｆ_W ＜３．５
ただし、ｆ₁ は第１群の焦点距離、ｆ_W は全系の広角端での焦点距離、Ｒ₂ は第１群の負メニスカスレンズの凹面の曲率半径である。
【００９１】
〔１１〕 物体側から順に、少なくとも負の屈折力を有する第１群、正の屈折力を有する第２群、負の屈折力を有する第３群、正の屈折力を有する第４群を含み、前記第１群が物体側から順に、負メニスカスレンズ、負レンズ、正レンズと負レンズとの接合からなる正メニスカスレンズ成分よりなり、少なくとも１面の非球面を含み、以下の条件を満足することを特徴とするズームレンズ。
【００９２】
（14） −４．０＜ｆ₁ ／ｆ_W ＜−１．５
（15） １．３＜Ｒ₂ ／ｆ_W ＜３．５
ただし、ｆ₁ は第１群の焦点距離、ｆ_W は全系の広角端での焦点距離、Ｒ₂ は第１群の負メニスカスレンズの凹面の曲率半径である。
【００９３】
〔１２〕 前記第１群の焦点距離の絶対値ｆ_1abs、前記第１群の後側主点位置の絶対値Ｈｂ_1absとしたとき、以下の条件を満たすことを特徴とする上記１から１１の何れか１項記載のズームレンズ。
【００９４】
（16） ０．１５＜Ｈｂ_1abs／ｆ_1abs＜０．９
〔１３〕 前記第１群と第２群に関して、以下の条件を満たすことを特徴とする上記１から１１の何れか１項記載のズームレンズ。
【００９５】
（17） ０．７×１０^-2ｍｍ^-1＜Ｈｂ_1abs／（ｆ_1abs・ｆ₂ ）
＜６×１０^-2ｍｍ^-1
ただし、ｆ_1absは第１群の焦点距離の絶対値、Ｈｂ_1absは第１群の後側主点位置の絶対値、ｆ₂ は第２群の焦点距離である。
【００９６】
〔１４〕 前記第３群が接合された凹レンズ成分と負の単レンズの２つのレンズ成分にて構成されており、以下の条件を満たすことを特徴とする上記１から１１の何れか１項記載のズームレンズ。
【００９７】
（18） ０．１＜ｆ₃₁／ｆ₃₂＜１
ただし、ｆ₃₁は第３群の接合された凹レンズ成分の焦点距離、ｆ₃₂は第３群の負の単レンズの焦点距離である。
【００９８】
〔１５〕 以下の条件式（１６）、（１７）、（１８）の中、複数の条件式を満足することを特徴とする上記１から１１の何れか１項記載のズームレンズ。
【００９９】
（16） ０．１５＜Ｈｂ_1abs／ｆ_1abs＜０．９
（17） ０．７×１０^-2ｍｍ^-1＜Ｈｂ_1abs／（ｆ_1abs・ｆ₂ ）
＜６×１０^-2ｍｍ^-1
（18） ０．１＜ｆ₃₁／ｆ₃₂＜１
ただし、ｆ_1absは第１群の焦点距離の絶対値、Ｈｂ_1absは第１群の後側主点位置の絶対値、ｆ₂ は第２群の焦点距離、ｆ₃₁は第３群の接合された凹レンズ成分の焦点距離、ｆ₃₂は第３群の負の単レンズの焦点距離である。
【０１００】
〔１６〕 広角端から望遠端にかけて変倍する際、第１群は広角端よりも望遠端にて像側に移動し、第２群と第４群が常に物体側に移動し、第３群が固定であることを特徴とする上記１から１５の何れか１項記載のズームレンズ。
【０１０１】
〔１７〕 前記第２群と第４群が一体に移動することを特徴とする上記１６記載のズームレンズ。
【０１０２】
〔１８〕 開口絞りを有し、該開口絞りが第２群と一体に移動するか又は第３群近傍に固定であることを特徴とする上記１から１７の何れか１項記載のズームレンズ。
【０１０３】
【発明の効果】
本発明によれ、特に電子撮像素子に対応した高性能大口径広角ズームレンズを提供することができる。また、特に電子撮像素子に対応した高性能大口径広角ズームレンズのフォーカシング方式を提供することができる。また、６００万画素クラスの小型電子撮像素子を用いた一眼レフ式カメラに適した広角端対角画角７５°（３５ｍｍ版換算で、焦点距離２８ｍｍクラス）で３倍クラスの高性能大口径広角ズームレンズを提供することができる。
【図面の簡単な説明】
【図１】本発明の実施例１のズームレンズの広角端でのレンズ配置を示す断面図である。
【図２】本発明の実施例２のズームレンズの広角端でのレンズ配置を示す断面図である。
【図３】本発明の実施例３のズームレンズの広角端でのレンズ配置を示す断面図である。
【図４】本発明の実施例４のズームレンズの広角端でのレンズ配置を示す断面図である。
【図５】実施例１の無限遠合焦時の収差図である。
【図６】実施例２の無限遠合焦時の収差図である。
【図７】実施例３の無限遠合焦時の収差図である。
【図８】実施例４の無限遠合焦時の収差図である。
【図９】本発明のズームレンズが適用可能な電子カメラの概略の構成を示す図である。
【図１０】本発明のズームレンズが適用可能なビデオカメラの概略の構成を示す図である。
【図１１】従来タイプのズームレンズで第１レンズ群をフォーカス群として用いた場合の概念図である。
【図１２】従来タイプのズームレンズで像側に負レンズ群を配置してこの群をフォーカス群として用いた場合の概念図である。
【図１３】本発明のズームレンズ構成を示す概念図である。
【符号の説明】
Ｇ１…第１群
Ｇ２…第２群
Ｇ３…第３群
Ｇ４…第４群
Ｇ５…第５群
Ｓ …絞り
１１…電子カメラ
１２…撮影用対物光学系
１３…ハーフミラープリズム
１４…ペンタプリズム
１５…接眼レンズ
１６…レリーズボタン
１７…ストロボ
１８…液晶表示モニタ
１９…ＣＣＤ
２０…コントローラ
２１…データ書き込み装置
２２…ローパスフィルター
２３…ＩＲカットフィルター
２４…ビデオカメラ
２５…ＬＣＤ（液晶表示素子）
２６…ＯＮ／ＯＦＦ切換えスイッチ
２７…録音マイク[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zoom lens, and more particularly to a zoom lens suitable for a camera using an electronic image sensor such as a CCD.
[0002]
[Prior art]
In recent years, digital cameras (electronic cameras) have attracted attention as next-generation cameras that replace silver salt 35 mm film (commonly known as Leica version) cameras. In particular, from a single focus lens having a diagonal angle of view of about 60 °, a zoom lens having a magnification of about 3 × with a wide angle end has become the mainstream in consumer lenses. In the higher class, the need for the wide-angle side or the telephoto side increases, and at the same time, the demand for high-end machines using a single-lens reflex system increases. Then, naturally high image quality is required. Among them, examples of zoom lenses suitable for a single-lens reflex camera with a diagonal field angle of 75 ° include Japanese Patent Laid-Open Nos. 4-163415 and 5-27175.
[0003]
These are, in order from the object side, a first group having negative refractive power, a second group having positive refractive power, a third group having negative refractive power, and a fourth group having positive refractive power, When zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group and the distance between the third group and the fourth group are decreased, the distance between the second group and the third group, and the image formation with the fourth group. A zoom lens is disclosed in which each group moves such that the spacing between the surfaces increases. Also, they have a bright F value of about 2 to 2.8 at the wide-angle end.
[0004]
However, at this time, even though it was a single-lens reflex camera, the number of pixels was only suggested to ensure performance of about 1 million pixels, and in the future, an electronic imaging device with the number of pixels said to be 6 million or 10 million. There is no suggestion of acquiring a lens that can fully demonstrate the performance of the lens.
[0005]
In addition, when trying to ensure performance, the size tends to increase naturally, which is also a problem to be solved.
[0006]
Further, regarding the focus, the rear focusing is desirable in consideration of the load and layout on the drive system and the effective diameter of the first group, but the first group having the negative refractive power described above has the positive refractive power. When rear focusing is performed with a zoom lens including the second group, the third group having a negative refractive power, and the fourth group having a positive refractive power, the problem of aberration variation or the magnification of the fourth group is A zoom region having a magnification equal to or close to the same magnification is included, which causes a problem that focusing is impossible or a large amount of movement of the focus group has to be secured.
[0007]
In JP-A-4-2641212 and JP-A-9-203861, the first group having the negative refractive power, the second group having the positive refractive power, the third group having the negative refractive power, and the positive refraction. The zoom lens is composed of a fourth lens group that has power and a positive fifth lens group that is fixed at the time of zooming. The four lens groups on the object side are responsible for zooming, and focusing There is no particular suggestion regarding.
[0008]
In JP-A-6-102455, the first group having negative refractive power, the second group having positive refractive power, the third group having negative refractive power, and the fourth group having positive refractive power. A rear focus zoom lens that is composed of a group and a negative fifth group that moves even during zooming and that performs focusing in the fifth group is presented. This optical system is also shown to move the fifth group to the image side during focusing from infinity to a short distance. When configuring an optical system corresponding to an electronic image pickup device such as a CCD that is required to be close to telecentric, it is not preferable that the lens group closest to the image side has a negative power because the entire optical system becomes thick.
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a high-performance large-aperture wide-angle zoom lens particularly compatible with an electronic image sensor. It is another object of the present invention to provide a focusing method for a high-performance large-aperture wide-angle zoom lens that is particularly compatible with electronic imaging devices. In addition, it is compatible with a single-lens reflex camera using a 6-megapixel class small electronic image sensor, and has a wide-angle end diagonal angle of view of 75 ° (35mm version equivalent, focal length of 28mm class) and a high-performance large aperture of 3x class. It is to provide a wide-angle zoom lens.
[0010]
[Means for Solving the Problems]
  The zoom lens of the present invention that achieves the above object includes, in order from the object side, a first group having negative refractive power, a second group having positive refractive power, a third group having negative refractive power, and positive refraction. A fourth group having power and a fifth group having positive refractive power,
  Zooming from the wide-angle end to the telephoto end is performed by reducing the interval between the first group and the second group and the interval between the third group and the fourth group, and the interval between the second group and the third group, and Increasing the distance between the fourth group and the imaging surface, decreasing the distance between the third group and the fifth group, and increasing the distance between the fifth group and the imaging surface;
  Focusing at the time of object point movement is performed by the fifth group. In this case, when focusing from a short distance to an infinity direction, the fifth group is moved to the image side, and from the infinity direction to the short distance direction. When focusing is performed, the fifth group is moved to the object side, and the following conditions are satisfied.
    (1) -0.2 <β_V<0.8
    (2) 0.6 <Δ_L5/ Δ_L4<1.2
    (3) 0.05 <D₄₅/ F_Five<0.15
However, β_VIs the magnification of the fifth group when focusing on an infinite object point at the wide angle end, Δ_L4Is the amount of movement from the wide-angle end to the telephoto end in the infinite object point in the fourth group, Δ_L5Is the amount of movement from the wide-angle end to the telephoto end in the infinite object point in the fifth group, D₄₅Is the air space on the optical axis between the fourth group and the fifth group at the time of focusing on an object point at infinity, f_FiveIs the focal length of the fifth group.
[0011]
Hereinafter, the reason and effect | action which take the said structure in this invention are demonstrated.
[0012]
As pointed out in the section of the prior art, the negative, positive, negative, and positive zoom lens configurations are types suitable for widening the angle. The function of the fourth group is divided into a fourth group having a positive refractive power and a fifth group having a positive refractive power to reduce fluctuations in aberrations at the time of zooming and telecentric without making the entire optical system thick. Invented a configuration that enables rear focusing (focusing with the lens group closest to the image side) with a small amount of movement, with a small amount of movement, and with little degradation in imaging performance during focusing, with a small amount of movement .
[0013]
11 to 13 are diagrams for explaining the operation of the present invention. FIG. 11 is a case in which the first lens group G1 of the conventional type is used as a focus group. The state shown in FIG. As apparent from the state of FIG. 11B in which the one lens group G1 is extended, it can be seen that the effective diameter of the first group G1 must be increased by focusing. FIG. 12 shows a case where a negative lens group G1 is arranged on the image side of a conventional type to form a negative, positive, negative, positive, and negative zoom lens configuration, and the first lens group G1 is used as a focus group, and is telecentric. In such an optical system, the effective diameter of the fourth group G4 must be increased. FIG. 13 shows the zoom lens configuration of the present invention, and it can be seen that this is an efficient optical system. Although not understood from FIG. 13, the variation of the off-axis aberrations such as astigmatism, coma and curvature of field is particularly reduced by the layout of the fourth group G4 and the fifth group G5 at the time of zooming. There is also an effect. The focus detection method may be performed by a triangulation method, a phase difference method, or the like, or may be performed by a contrast method based on information from an image sensor.
[0014]
In the present invention, if any of the following conditions is satisfied, it is preferable because the advantages of rear focus can be easily obtained.
[0015]
(1) -0.2 <β_V<0.8
(2) 0.6 <Δ_L5/ Δ_L4<1.2
(3) 0.05 <D₄₅/ F_Five<0.15
However, β_VIs the magnification of the fifth lens group when focusing on an infinite object point at the wide angle end, Δ_L4Is the amount of movement from the wide-angle end to the telephoto end in the infinite object point in the fourth group, Δ_L5Is the amount of movement from the wide-angle end to the telephoto end in the infinite object point in the fifth group, D₄₅Is the air space on the optical axis between the fourth group and the fifth group at the time of focusing on an object point at infinity, f_FiveThis is the focal length of the fifth group.
[0016]
Moreover, it is better if each of the following conditions is satisfied separately.
[0017]
(1 ') 0 <β_V<0.7
(2 ') 0.7 <Δ_L5/ Δ_L4<1.1
(3 ') 0.06 <D₄₅/ F_Five<0.12
It is best if each of the following conditions is satisfied separately.
[0018]
(1 ") 0.2 <β_V<0.6
(2 ") 0.8 <Δ_L5/ Δ_L4<1.05
(3 ") 0.07 <D₄₅/ F_Five<0.1
The above condition (1) is that the magnification β of the fifth group at the time of focusing on the infinite object point at the wide angle end_VIt prescribes. If the upper limit of 0.8 is exceeded, the amount of movement at the time of focusing tends to be large, which requires a lot of space and is not preferable. If the lower limit of −0.2 is exceeded, the power of the fifth lens group tends to increase and the diameter tends to increase.
[0019]
Condition (2) is that the amount of movement from the wide-angle end to the telephoto end in the infinite object point focusing state of the fourth group and the fifth group (each Δ_L4, Δ_L5) Ratio. The amount of movement of the focus group (fifth group) during focusing on a short-distance object point is approximately the square of the zoom ratio at the telephoto end with respect to the wide-angle end, and is 1.2 or less, the upper limit. More preferably, the upper limit is made smaller than 1. It is still more preferable if it is 0.9 or less. On the other hand, the zooming function of this zoom lens plays a part in the 4th and 5th composing group approaching the 3rd group, and it is one of the main roles, but it exceeds the lower limit of 0.6. If this is the case, the proximity of the principal points of the fourth and fifth composite groups cannot be sufficiently obtained for the approach of the fourth group to the third group, which is undesirable because the zooming effect is reduced.
[0020]
Condition (3) is that the air distance D on the optical axis between the fourth group and the fifth group at the time of focusing on an object point at infinity at the telephoto end.₄₅It prescribes. Exceeding the upper limit of 0.15 is not preferable, for example, because the zoom ratio decreases or the entire length becomes long, and the variation of the exit pupil position during zooming tends to increase. If the lower limit of 0.05 is exceeded, the focus stroke is insufficient and short-distance shooting cannot be performed.
[0021]
The fifth group has a focusing function, but it is not preferable that the aberration variation due to focusing is large. Further, the fifth group also has a role of securing the exit side telecentricity. Furthermore, it is also a group in which off-axis aberrations are likely to occur. Therefore, it is preferable that the fifth group is composed of a positive single lens component including an aspherical surface, or two lenses of a negative lens and a positive lens (which may be a positive cemented lens component). Alternatively, the radius of curvature of the most object side surface of the fifth group is R₅₁, The radius of curvature of the most image side surface is R₅₂When
(4) -2 <(R₅₁+ R₅₂) / (R₅₁-R₅₂<0.2
Or
(4 ') -1.5 <(R₅₁+ R₅₂) / (R₅₁-R₅₂) <0
Or
(4 ") -1.2 <(R₅₁+ R₅₂) / (R₅₁-R₅₂) <-0.2
It is preferable to satisfy Even if this range is deviated in any direction, the axial aberration and the off-axis aberration are not balanced, and it is difficult to obtain flat characteristics over the entire effective screen.
[0022]
The high-performance large-aperture wide-angle zoom lens according to the second aspect of the present invention will be described below.
[0023]
The zoom lens includes, in order from the object side, a first group having at least negative refractive power, a second group having positive refractive power, a third group having negative refractive power, and a fourth group having positive refractive power. The first lens unit includes, in order from the object side, a positive lens, a negative meniscus lens, and a negative lens component formed by joining a negative lens and a positive meniscus lens. This ensures image forming performance.
[0024]
(5) -4.0 <f₁/ F_W<-1.5
(6) 1.55 <n₁<1.8
(7) 1.3 <R_Four/ F_W<3.5
(8) 37 <ν₁<83
Where f₁Is the focal length of the first group, f_WIs the focal length at the wide-angle end of the entire system, n₁Is the medium refractive index of the positive lens closest to the object side in the first group, R_FourIs the radius of curvature of the concave surface of the negative meniscus lens of the first group, ν₁Is the medium Abbe number of the positive lens closest to the object side in the first group.
[0025]
Alternatively, it is preferable if the following conditions are satisfied separately.
[0026]
(5 ') -3.5 <f₁/ F_W<-1.6
(6 ') 1.6 <n₁<1.8
(7 ') 1.5 <R_Four/ F_W<3
(8 ') 39 <ν₁<65
Alternatively, it is more preferable if the following conditions are satisfied separately.
[0027]
(5 ") -3.2 <f₁/ F_W<-1.7
(6 ") 1.65 <n₁<1.8
(7 ") 1.7 <R_Four/ F_W<2.5
(8 ") 45 <ν₁<56
Condition (5) is the focal length f of the entire first group.₁Is the focal length f at the wide-angle end of the entire system._WIt is specified in. If the upper limit of −1.5 is exceeded, the radius of curvature of the concave surface of the negative meniscus lens must be made extremely small, making it difficult to construct as a lens, and at the same time, off-axis aberrations tend to deteriorate. If the lower limit of −4.0 is exceeded, it is advantageous for aberration correction, but the entrance pupil is likely to be deep (that is, the entrance pupil position is likely to be arranged toward the image plane side), and the first group diameter is likely to be enlarged. .
[0028]
Condition (6) is that the medium refractive index n of the positive lens closest to the object side in the first group₁It is a rule about. The high performance large aperture wide angle zoom lens of the present invention tends to be negative Petzval sum. When the upper limit of 1.8 is exceeded, it becomes a disadvantageous direction for Petzval sum correction, and astigmatism tends to deteriorate. When the lower limit of 1.55 is exceeded, high-order aberrations tend to occur at large angles of view.
[0029]
Condition (7) is that the radius of curvature R of the concave surface of the negative meniscus lens of the first group_FourIs specified. The power of this surface is dominant with respect to the power of the entire first lens group, and is also dominant with respect to the entrance pupil position. When the upper limit of 3.5 is exceeded, the entrance pupil tends to be deep, and the first group diameter tends to become large. If the lower limit of 1.3 is exceeded, it is difficult to construct a lens, and at the same time, off-axis aberrations tend to deteriorate.
[0030]
Condition (8) is that the medium Abbe number ν of the positive lens closest to the object side in the first group₁It is a rule about. Exceeding the upper limit of 83 makes it difficult to correct axial chromatic aberration and lateral chromatic aberration (transverse aberration component proportional to image height), and exceeding the lower limit of 37 adds significant nonlinearity (color distortion) to lateral chromatic aberration. A significant color shift tends to occur at the periphery of the screen.
[0031]
The high-performance large-aperture wide-angle zoom lens according to the third aspect of the present invention will be described below.
[0032]
The zoom lens includes, in order from the object side, a first group having at least negative refractive power, a second group having positive refractive power, a third group having negative refractive power, and a fourth group having positive refractive power. In order from the object side, the first group includes a positive lens, a negative meniscus lens, a negative lens, and a positive meniscus lens. Further, in order to reduce the first group diameter which tends to be large, the first group Distance D between negative lens and positive meniscus lens₆In addition, the present invention relates to a large-aperture, wide-angle zoom lens that satisfies the condition (9) and satisfies the conditions (10) to (13).
[0033]
(9) 0.5 <D₆/ F_W<1.2
(10) -4.0 <f₁/ F_W<-1.5
(11) 1.55 <n₁<1.8
(12) 1.3 <R_Four/ F_W<3.5
(13) 37 <ν₁<83
However, D₆Is the distance between the negative lens in the first group and the positive meniscus lens, f₁Is the focal length of the first group, f_WIs the focal length at the wide-angle end of the entire system, n₁Is the medium refractive index of the positive lens closest to the object side in the first group, R_FourIs the radius of curvature of the concave surface of the negative meniscus lens of the first group, ν₁Is the medium Abbe number of the positive lens closest to the object side in the first group.
[0034]
Alternatively, it is preferable if the following conditions are satisfied separately.
[0035]
(9 ') 0.6 <D₆/ F_W<1.1
(10 ') -3.5 <f₁/ F_W<-1.6
(11 ') 1.6 <n₁<1.8
(12 ') 1.5 <R_Four/ F_W<3
(13 ') 39 <ν₁<65
Alternatively, it is more preferable if the following conditions are satisfied separately.
[0036]
(9 ") 0.7 <D₆/ F_W<1.0
(10 ") -3.2 <f₁/ F_W<-1.7
(11 ") 1.65 <n₁<1.8
(12 ") 1.7 <R_Four/ F_W<2.5
(13 ") 45 <ν₁<56
If the lower limit of 0.5 of the condition (9) is exceeded, the first group diameter tends to increase, and if the upper limit of 1.2 is exceeded, the first group diameter can be reduced, but the originally small second group diameter increases. In the beginning, it is difficult to secure a rim, or it tends to cause enormous lens enlargement and performance deterioration.
[0037]
Conditions (10) to (13) are the same as the conditions (5) to (8) of the second invention.
[0038]
  The high performance large aperture wide angle zoom lens according to the fourth aspect of the present invention will be described below. This invention is a reference example of the present invention.
[0039]
  The zoom lens includes, in order from the object side, a first group having at least negative refractive power, a second group having positive refractive power, a third group having negative refractive power, and a fourth group having positive refractive power. The first lens unit is composed of, in order from the object side, a negative meniscus lens, a negative lens, a negative lens component composed of a cemented positive lens and a negative lens, and a large-aperture wide-angle zoom lens that satisfies the following conditions: is there.
[0040]
(14) -4.0 <f₁/ F_W<-1.5
(15) 1.3 <R₂/ F_W<3.5
Where f₁Is the focal length of the first group, f_WIs the focal length at the wide-angle end of the entire system, R₂Is the radius of curvature of the concave surface of the negative meniscus lens of the first group.
[0041]
Alternatively, it is preferable if the following conditions are satisfied separately.
[0042]
(14 ') -3.5 <f₁/ F_W<-1.6
(15 ') 1.5 <R₂/ F_W<3
Alternatively, it is more preferable if the following conditions are satisfied separately.
[0043]
(14 ") -3.2 <f₁/ F_W<-1.7
(15 ") 1.7 <R₂/ F_W<2.5
The reason for condition (14) is that conditions (5) and (10) and the radius of curvature R of the concave surface of the negative meniscus lens of the first group₂The reason for the condition (15) for prescribing is the same as the conditions (7) and (12).
[0044]
In addition to the above configuration, by adding at least one aspheric surface to the first group, it is possible to improve the imaging performance without changing the number of components.
[0045]
For each of the above-described inventions, aberration correction will be better if the refractive index arrangement is as follows. Absolute value f of the focal length of the first group_1absThe absolute value Hb of the rear principal point position of the first group (the distance on the optical axis between the rear principal point of the first group and the most image side surface of the first group)._1absThe following conditions should be satisfied.
[0046]
(16) 0.15 <Hb_1abs/ F_1abs<0.9
Or
(16 ') 0.2 <Hb_1abs/ F_1abs<0.8
Or
(16 ") 0.25 <Hb_1abs/ F_1abs<0.7
If the upper limit of 0.9 in condition (16) is exceeded, the height of the incident light beam on the second group becomes too high, and it becomes difficult to ensure the thickness of the positive lens in the second group and to correct spherical aberration. When the lower limit of 0.15 is exceeded, the entrance pupil becomes too deep and the front lens diameter tends to increase.
[0047]
Next, the following conditions should be satisfied in the mutual relationship between the first group and the second group. Where f₂Is the focal length of the second group.
[0048]
    (17) 0.7 × 10^-2mm^-1<Hb_1abs/ (F_1abs・ F₂)
                                                    <6 × 10^-2mm^-1
  Or
    (17 ') 0.8 × 10^-2mm^-1<Hb_1abs/ (F_1abs・ F₂)
                                                    <5 × 10^-2mm^-1
  Or
    (17 ") 0.9 × 10^-2mm^-1<Hb_1abs/ (F_1abs・ F₂)
                                                    <4x10^-2mm^-1
  Upper limit 6 × 10 of condition (17)^-2mm^-1Beyond, the variation of spherical aberration at the time of zooming, especially the chromatic spherical aberration, tends to be large. Lower limit of 0.7 × 10^-2mm^-1If it exceeds, the total length and the front lens diameter tend to be large.
[0049]
The third group is preferably composed of two lens components, a cemented concave lens component and a negative single lens, and satisfies the following conditions.
[0050]
(18) 0.1 <f₃₁/ F₃₂<1
Where f₃₁Is the focal length of the cemented concave lens component of the third group, f₃₂Is the focal length of the third group negative single lens.
[0051]
Or
(18 ') 0.2 <f₃₁/ F₃₂<0.9
Or
(18 ") 0.3 <f₃₁/ F₃₂<0.8
If the upper limit value 1 of the condition (18) is exceeded, the principal ray height to the fourth group becomes high, and it becomes difficult to correct off-axis aberrations. If the lower limit of 0.1 is exceeded, spherical aberrations in the third lens group, particularly chromatic spherical aberrations, tend to increase.
[0052]
It is still better to satisfy a plurality of the above three conditions (16), (17), and (18). Of course, instead of (16), (16 '), (16 "), or (17') instead of (17 '), (17"), or (18') instead of (18 '), ( There is a change such as 18 ").
[0053]
Further, what can be said in common from the first invention to the fourth invention is that when zooming from the wide-angle end to the telephoto end, the first group moves to the image side at the telephoto end rather than the wide-angle end, and the second A zoom method in which the group and the fourth group always move toward the object side and the third group is fixed is preferable. Further, it is advantageous in terms of the lens frame configuration that the second group and the fourth group move together, and it is easy to establish optically. The aperture stop position is preferably fixed in the vicinity of the third group, that is, in the air gap on the object side or the image side of the third group, or in the third group. The aperture stop may be integrated with the second group.
[0054]
Each configuration described above is suitable for a zoom lens having a zoom ratio of 2.7 or more. In addition, each configuration is suitable for a zoom lens having an angle of view 2ω at the wide angle end of 70 ° or more. In addition, each configuration is suitable for a bright zoom lens having an F-number when the aperture stop is fully opened, which is 3.5 or less and further 2.8 or less in the entire zoom range.
[0055]
DETAILED DESCRIPTION OF THE INVENTION
  Next, first to fourth embodiments of the zoom lens according to the present invention will be described. The lens data of the zoom lens of each embodiment will be described later. The unit of length is mm. Example 4 is a reference example of the present invention.
[0056]
1 to 4 are sectional views showing the lens arrangement at the wide-angle end of the zoom lenses of Examples 1 to 4. FIG. The movement trajectory accompanying zooming from the wide-angle end to the telephoto end of each group is also schematically shown by arrows. 1 to 4, in each case, three parallel flat plates are arranged between the fifth group G5 and the image plane. These are, in order from the object side, a viewfinder split prism, a low-pass filter, IR cut filter.
[0057]
Example 1 is a zoom lens having a focal length of 7.00 to 21.00, an angle of view of 76.3 ° to 29.4 °, and an F number of 2.04 to 2.73. As shown in FIG. The first group G1 includes a positive meniscus lens having a convex surface facing the object side, a negative meniscus lens having a convex surface facing the object side, and a cemented lens of a biconcave negative lens and a positive meniscus lens having a convex surface facing the object side. The second group G2 is composed of a cemented lens of a biconcave negative lens and a biconvex positive lens, and a biconvex positive lens, after which the stop S is located, and the third group G3 is convex on the image side. The fourth lens group G4 is composed of one biconvex positive lens, and the fifth lens group G5 has a convex surface on the image side with the biconvex positive lens. It consists of a cemented lens with a negative meniscus lens. The aspherical surfaces are three surfaces: the object side surface of the cemented lens of the first group G1, the object side surface of the biconvex positive lens of the second group G2, and the image side surface of the biconvex positive lens of the fourth group G4. It is used for. During zooming from the wide-angle end to the telephoto end, as indicated by an arrow in the figure, the stop S and the third group G3 are fixed, the first group G1 moves to the image plane side, and the second group G2 moves to the object side. The fourth group G4 and the fifth group G5 move to the object side. Meanwhile, the distance between the first group G1 and the second group G2, the distance between the third group G3 and the fourth group G4, and the distance between the third group G3 and the fifth group G5 are reduced, and the second group G2 and The distance between the third group G3, the distance between the fourth group G4 and the image plane, and the distance between the fifth group G5 and the image plane increase. Focusing at the time of moving the object point is performed by the fifth group G5. At this time, when focusing from the infinity direction to the short distance direction, the object side is moved.
[0058]
Example 2 is a zoom lens having a focal length of 7.00 to 21.00, an angle of view of 76.3 ° to 29.4 °, and an F number of 2.01 to 2.54. As shown in FIG. The first group G1 includes a positive meniscus lens having a convex surface facing the object side, a negative meniscus lens having a convex surface facing the object side, and a cemented lens of a biconcave negative lens and a positive meniscus lens having a convex surface facing the object side. The second group G2 is composed of a cemented lens of a biconcave negative lens and a biconvex positive lens, and a biconvex positive lens, after which the stop S is located, and the third group G3 is convex on the image side. The fourth group G4 is composed of a cemented lens of a negative meniscus lens having a convex surface directed toward the object side and a biconvex positive lens, and has a fifth group G5. Consists of one biconvex positive lens. The aspherical surfaces are three surfaces: the object side surface of the cemented lens of the first group G1, the object side surface of the biconvex positive lens of the second group G2, and the object side surface of the biconvex positive lens of the fifth group G5. It is used. During zooming from the wide-angle end to the telephoto end, as indicated by an arrow in the figure, the stop S and the third group G3 are fixed, the first group G1 moves to the image plane side, and the second group G2 moves to the object side. The fourth group G4 and the fifth group G5 move to the object side. Meanwhile, the distance between the first group G1 and the second group G2, the distance between the third group G3 and the fourth group G4, and the distance between the third group G3 and the fifth group G5 are reduced, and the second group G2 and The distance between the third group G3, the distance between the fourth group G4 and the image plane, and the distance between the fifth group G5 and the image plane increase. Focusing at the time of moving the object point is performed by the fifth group G5. At this time, when focusing from the infinity direction to the short distance direction, the object side is moved.
[0059]
Example 3 is a zoom lens having a focal length of 7.00 to 21.00, an angle of view of 76.3 ° to 29.4 °, and an F number of 2.01 to 3.17. As shown in FIG. The first group G1 includes a biconvex positive lens having a strong convex surface facing the object side, a negative meniscus lens having a convex surface facing the object side, a biconcave negative lens, and a positive meniscus lens having a convex surface facing the object side. The second group G2 is composed of a cemented lens of a biconcave negative lens and a biconvex positive lens, and a biconvex positive lens, after which the stop S is located, and the third group G3 has a convex surface on the image side. The fourth lens group G4 is composed of a cemented lens composed of a biconcave negative lens and a biconvex positive lens, and is composed of a cemented lens composed of a positive meniscus lens and a biconcave negative lens. G5 includes one positive meniscus lens having a convex surface facing the object side. The aspherical surfaces are the object side surface of the biconcave negative lens of the first group G1, the object side surface of the biconvex positive lens of the second group G2, and the object side surface of the biconvex positive lens of the fifth group G5. Used on the surface. During zooming from the wide-angle end to the telephoto end, as indicated by an arrow in the figure, the stop S and the third group G3 are fixed, the first group G1 moves to the image plane side, and the second group G2 moves to the object side. The fourth group G4 and the fifth group G5 move to the object side. Meanwhile, the distance between the first group G1 and the second group G2, the distance between the third group G3 and the fourth group G4, and the distance between the third group G3 and the fifth group G5 are reduced, and the second group G2 and The distance between the third group G3, the distance between the fourth group G4 and the image plane, and the distance between the fifth group G5 and the image plane increase. Focusing at the time of moving the object point is performed by the fifth group G5. At this time, when focusing from the infinity direction to the short distance direction, the object side is moved.
[0060]
Example 4 is a zoom lens having a focal length of 7.00 to 21.00, an angle of view of 76.3 ° to 29.4 °, and an F number of 2.01 to 2.82. As shown in FIG. The first group G1 includes two negative meniscus lenses having a strong convex surface facing the object side, and a cemented lens of a positive meniscus lens having a convex surface facing the image surface side and a biconcave negative lens. It consists of a cemented lens composed of a negative meniscus lens having a convex surface facing the image surface side and a positive meniscus lens having a convex surface facing the image surface side, and a biconvex positive lens. The fourth lens unit G4 includes a cemented lens of a positive meniscus lens having a convex surface facing the image surface and a biconcave negative lens, and a negative meniscus lens having a convex surface facing the image surface. The fourth group G4 has a strong convex surface on the object side. A negative meniscus lens and a biconvex positive lens, It consists of The aspherical surface is a surface on the image side of the second negative meniscus lens in the first group G1, an object side surface of the biconvex positive lens in the second group G2, and an object side of the biconvex positive lens in the fourth group G4. It is used for three surfaces. During zooming from the wide-angle end to the telephoto end, as indicated by an arrow in the figure, the stop S and the third group G3 are fixed, the first group G1 moves to the image plane side, and the second group G2 moves to the object side. The fourth group G4 moves to the object side. Meanwhile, the distance between the first group G1 and the second group G2, and the distance between the third group G3 and the fourth group G4 are decreased, the distance between the second group G2 and the third group G3, and the fourth group G4. The image plane spacing increases. When focusing from the infinity direction to the short distance direction, the focus at the time of moving the object point is such that, at the wide-angle end, the distance between the first group G1 and the second to fourth groups G2 to G4 is reduced. The first group G1 is moved to the object side at the intermediate focal length and at the telephoto end.
[0061]
The lens data for each of the above examples is shown below, where the symbol is outside the above, f is the total focal length, F_NOIs the F number, 2ω is the angle of view, r₁, R₂... is the radius of curvature of each lens surface, d₁, D₂... is the distance between each lens surface, n_d1, N_d2... is the refractive index of d-line of each lens, ν_d1, Ν_d2... Is the Abbe number of the d-line of each lens. The aspherical shape is expressed by the following expression, where x is an optical axis with the traveling direction of light as positive and y is in a direction perpendicular to the optical axis.
[0062]

Where r is the paraxial radius of curvature, K is the cone coefficient, A_Four, A₆, A₈, A_TenAre the 4th, 6th, 8th and 10th order aspherical coefficients, respectively.
[0063]

[0064]

[0065]

[0066]

[0067]
Aberration diagrams at the time of focusing on infinity in Examples 1 to 4 are shown in FIGS. In each aberration diagram, (a) shows the aberration at the wide-angle end, (b) shows the aberration at the intermediate focal length, and (c) shows the aberration at the telephoto end. In these figures, SA is spherical aberration, AS is astigmatism, DT is distortion, and CC is lateral chromatic aberration. Note that FIY is the image height.
[0068]
Next, parameter values relating to the conditional expressions (1) to (18) of Examples 1 to 4 are shown in the following table.
[0069]

[0070]
Moreover, the value regarding the other conditional expression of the said Examples 1-4 is shown next.
Example 1
Δ_L5/ Δ_L4                        1.004
D₄₅/ F_Five                        0.0838
(R₅₁+ R₅₂) / (R₅₁-R₅₂-0.346
f₁/ F_W                      -2.89
R_Four/ F_W                        2.342
Hb_1abs/ F_1abs                  0.278
Hb_1abs/ (F_1abs・ F₂0.0107
Scaling ratio 3.0
Wide angle end angle of view 2ω 76.3 °
Example 2
Δ_L5/ Δ_L4                        0.991
D₄₅/ F_Five                        0.0887
(R₅₁+ R₅₂) / (R₅₁-R₅₂-0.556
f₁/ F_W                      -2.755
R_Four/ F_W                        2.243
Hb_1abs/ F_1abs                  0.283
Hb_1abs/ (F_1abs・ F₂0.0118
Scaling ratio 3.0
Wide angle end angle of view 2ω 76.3 °
Example 3
Δ_L5/ Δ_L4                        0.987
D₄₅/ F_Five                        0.0873
(R₅₁+ R₅₂) / (R₅₁-R₅₂-1.076
f₁/ F_W                      -1.864
R_Four/ F_W                        1.839
D₆/ F_W                        0.857
Hb_1abs/ F_1abs                  0.683
Hb_1abs/ (F_1abs・ F₂0.0380
f₃₁/ F₃₂                        0.738
Scaling ratio 3.0
Wide angle end angle of view 2ω 76.3 °
Example 4
f₁/ F_W                      -2.235
R₂/ F_W                        2.024
Hb_1abs/ F_1abs                  0.520
Hb_1abs/ (F_1abs・ F₂0.0279
f₃₁/ F₃₂                        0.327
Scaling ratio 3.0
Wide angle end angle of view 2ω 76.3 °.
[0071]
The large-aperture wide-angle zoom lens of the present invention as described above can be used, for example, in a photographing objective optical system 12 of an electronic camera 11 as shown in FIG. 9A is a perspective view of the electronic camera 11 viewed from the front side, FIG. 9B is a perspective view of the electronic camera 11 viewed from the rear side, and FIG. 9C is an optical path diagram illustrating the optical system of the electronic camera 11. The electronic camera 11 includes a photographing optical system 12 having a photographing optical path, a half mirror prism 13 disposed in the optical path of the photographing optical system 12 and separating the optical path for the finder, and a finder for the finder formed by the half mirror prism 13. A pentaprism 14 having a roof reflecting surface for erecting an image, an eyepiece lens 15, a release button 16, a strobe 17, a liquid crystal display monitor 18, a CCD 19, and a controller 20 for converting an image incident on the CCD 19 into an electric signal, a captured image A data writing device 21 that records data on a recording medium (for example, a PC card) that electrically records the data is included.
[0072]
In the optical path of the photographing optical system 12, a low-pass filter 22 and an IR cut filter 23 are arranged on the CCD 19 side of the half mirror prism 13.
[0073]
In addition, the large-aperture wide-angle zoom lens of the present invention can be used for a photographing objective optical system 12 of a video camera 24 (conceptual diagram) as shown in FIG. 10, for example. FIG. 10 is an optical path diagram showing the optical system of the video camera 24. The video camera 24 displays the image taken by the image taking optical system 12, the image taking optical system 12 having an image taking optical path, and the image taken by the CCD 19. LCD (liquid crystal display element) 25, eyepiece 15 for guiding the image from LCD 25 to the observer's eyeball, photographing ON / OFF switch 26, recording microphone 27, liquid crystal display monitor 18, and image incident on CCD 19 as an electrical signal And a data writing device 21 that can be recorded on a recording medium (for example, magnetic tape, digital video tape, DVD) that electrically records the captured image.
[0074]
A low-pass filter 22 and an IR cut filter 23 are arranged in the optical path of the photographing optical system 12.
[0075]
The zoom lens of the present invention described above can be configured as follows, for example.
[0076]
[1] In order from the object side, a first group having negative refractive power, a second group having positive refractive power, a third group having negative refractive power, a fourth group having positive refractive power, a positive group A zoom lens comprising a fifth lens unit having refractive power, and focusing when moving an object point is performed by the fifth lens unit.
[0077]
[2] In order from the object side, a first group having negative refractive power, a second group having positive refractive power, a third group having negative refractive power, a fourth group having positive refractive power, a positive group It consists of a fifth group having a refractive power, and zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group and the distance between the third group and the fourth group are decreased, and the second group and the third group are reduced. The zoom lens according to claim 5, wherein the distance between the groups and the distance between the fourth group and the imaging surface are increased, and focusing at the time of object point movement is performed in the fifth group.
[0078]
[3] In order from the object side, a first group having negative refractive power, a second group having positive refractive power, a third group having negative refractive power, a fourth group having positive refractive power, a positive group It consists of a fifth group having a refractive power, and zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group and the distance between the third group and the fourth group are decreased, and the second group and the third group The distance between the groups and the distance between the fourth group and the imaging plane are increased, and the focusing at the time of moving the object point is performed in the fifth group. In this case, when focusing from the short distance to the infinity direction, A zoom lens, wherein the fifth group is moved to the object side when the group is moved to the image side and when focusing is performed from the infinity direction to the short distance direction.
[0079]
[4] In order from the object side, a first group having a negative refractive power, a second group having a positive refractive power, a third group having a negative refractive power, a fourth group having a positive refractive power, a positive Consisting of a fifth group having refractive power, the zooming from the wide-angle end to the telephoto end is reduced, and the distance between the first group and the second group and the distance between the third group and the fourth group and the third group and the fifth group are decreased. The distance between the second group and the third group, the distance between the fourth group and the imaging surface, and the distance between the fifth group and the imaging surface are increased, and the subject is focused by moving the fifth group. Zoom lens.
[0080]
[5] In order from the object side, a first group having a negative refractive power, a second group having a positive refractive power, a third group having a negative refractive power, a fourth group having a positive refractive power, and a positive A zoom lens comprising a fifth lens unit having refractive power, and satisfying the following condition in an optical system for focusing on object movement in the fifth lens unit.
[0081]
(1) -0.2 <β_V<0.8
(2) 0.6 <Δ_L5/ Δ_L4<1.2
(3) 0.05 <D₄₅/ F_Five<0.15
However, β_VIs the magnification of the fifth lens group when focusing on an infinite object point at the wide angle end, Δ_L4Is the amount of movement from the wide-angle end to the telephoto end in the infinite object point in the fourth group, Δ_L5Is the amount of movement from the wide-angle end to the telephoto end in the infinite object point in the fifth group, D₄₅Is the air space on the optical axis between the fourth group and the fifth group at the time of focusing on an object point at infinity, f_FiveThis is the focal length of the fifth group.
[0082]
[6] The zoom lens according to any one of [1] to [5], wherein the fifth group includes a positive single lens component including an aspherical surface or a cemented positive lens component.
[0083]
[7] The zoom lens according to any one of [1] to [6], wherein the fifth group includes a positive lens component, and a shape factor of the positive lens component satisfies the following condition.
[0084]
(4) -2 <(R₅₁+ R₅₂) / (R₅₁-R₅₂<0.2
However, R₅₁Is the radius of curvature of the most object-side surface of the fifth group, R₅₂Is the radius of curvature of the fifth image side most image side surface.
[0085]
[8] In order from the object side, including at least a first group having negative refractive power, a second group having positive refractive power, a third group having negative refractive power, and a fourth group having positive refractive power The zoom lens according to claim 1, wherein the first lens unit includes, in order from the object side, a positive lens, a negative meniscus lens, and a negative lens component formed by joining a negative lens and a positive meniscus lens, and satisfies the following conditions.
[0086]
(5) -4.0 <f₁/ F_W<-1.5
(6) 1.55 <n₁<1.8
(7) 1.3 <R_Four/ F_W<3.5
(8) 37 <ν₁<83
Where f₁Is the focal length of the first group, f_WIs the focal length at the wide-angle end of the entire system, n₁Is the medium refractive index of the positive lens closest to the object side in the first group, R_FourIs the radius of curvature of the concave surface of the negative meniscus lens of the first group, ν₁Is the medium Abbe number of the positive lens closest to the object side in the first group.
[0087]
[9] In order from the object side, including at least a first group having negative refractive power, a second group having positive refractive power, a third group having negative refractive power, and a fourth group having positive refractive power The zoom lens according to claim 1, wherein the first group includes a positive lens, a negative meniscus lens, a negative lens, and a positive meniscus lens in order from the object side, and satisfies the following conditions.
[0088]
(9) 0.5 <D₆/ F_W<1.2
(10) -4.0 <f₁/ F_W<-1.5
(11) 1.55 <n₁<1.8
(12) 1.3 <R_Four/ F_W<3.5
(13) 37 <ν₁<83
However, D₆Is the distance between the negative lens in the first group and the positive meniscus lens, f₁Is the focal length of the first group, f_WIs the focal length at the wide-angle end of the entire system, n₁Is the medium refractive index of the positive lens closest to the object side in the first group, R_FourIs the radius of curvature of the concave surface of the negative meniscus lens of the first group, ν₁Is the medium Abbe number of the positive lens closest to the object side in the first group.
[0089]
[10] In order from the object side, at least a first group having negative refractive power, a second group having positive refractive power, a third group having negative refractive power, and a fourth group having positive refractive power The zoom lens according to claim 1, wherein the first lens unit includes, in order from the object side, a negative meniscus lens, a negative lens, and a positive meniscus lens component formed by joining a positive lens and a negative lens, and satisfies the following conditions.
[0090]
(14) -4.0 <f₁/ F_W<-1.5
(15) 1.3 <R₂/ F_W<3.5
Where f₁Is the focal length of the first group, f_WIs the focal length at the wide-angle end of the entire system, R₂Is the radius of curvature of the concave surface of the negative meniscus lens of the first group.
[0091]
[11] In order from the object side, including at least a first group having negative refractive power, a second group having positive refractive power, a third group having negative refractive power, and a fourth group having positive refractive power The first group includes, in order from the object side, a negative meniscus lens, a negative lens, and a positive meniscus lens component formed by joining a positive lens and a negative lens, and includes at least one aspheric surface, and satisfies the following conditions: A zoom lens characterized by that.
[0092]
(14) -4.0 <f₁/ F_W<-1.5
(15) 1.3 <R₂/ F_W<3.5
Where f₁Is the focal length of the first group, f_WIs the focal length at the wide-angle end of the entire system, R₂Is the radius of curvature of the concave surface of the negative meniscus lens of the first group.
[0093]
[12] The absolute value f of the focal length of the first group_1abs, Absolute value Hb of the rear principal point position of the first group_1absThe zoom lens according to any one of 1 to 11, wherein the following condition is satisfied:
[0094]
(16) 0.15 <Hb_1abs/ F_1abs<0.9
[13] The zoom lens according to any one of 1 to 11, wherein the following condition is satisfied with respect to the first group and the second group.
[0095]
    (17) 0.7 × 10^-2mm^-1<Hb_1abs/ (F_1abs・ F₂)
                                                    <6 × 10^-2mm^-1
Where f_1absIs the absolute value of the focal length of the first group, Hb_1absIs the absolute value of the rear principal point position of the first group, f₂Is the focal length of the second group.
[0096]
[14] Any one of [1] to [11], wherein the third group includes a cemented concave lens component and a negative single lens, and satisfies the following condition: Zoom lens.
[0097]
(18) 0.1 <f₃₁/ F₃₂<1
Where f₃₁Is the focal length of the cemented concave lens component of the third group, f₃₂Is the focal length of the third group negative single lens.
[0098]
[15] The zoom lens as described in any one of 1 to 11 above, wherein a plurality of conditional expressions among the following conditional expressions (16), (17) and (18) are satisfied.
[0099]
    (16) 0.15 <Hb_1abs/ F_1abs<0.9
    (17) 0.7 × 10^-2mm^-1<Hb_1abs/ (F_1abs・ F₂)
                                                    <6 × 10^-2mm^-1
    (18) 0.1 <f₃₁/ F₃₂<1
Where f_1absIs the absolute value of the focal length of the first group, Hb_1absIs the absolute value of the rear principal point position of the first group, f₂Is the focal length of the second group, f₃₁Is the focal length of the cemented concave lens component of the third group, f₃₂Is the focal length of the third group negative single lens.
[0100]
[16] When zooming from the wide-angle end to the telephoto end, the first group moves to the image side at the telephoto end rather than the wide-angle end, and the second and fourth groups always move to the object side, and the third group 16. The zoom lens according to any one of 1 to 15, wherein is fixed.
[0101]
[17] The zoom lens as described in 16 above, wherein the second group and the fourth group move together.
[0102]
[18] The zoom lens according to any one of 1 to 17, wherein the zoom lens has an aperture stop, and the aperture stop moves integrally with the second group or is fixed in the vicinity of the third group.
[0103]
【The invention's effect】
According to the present invention, it is possible to provide a high-performance large-aperture wide-angle zoom lens particularly compatible with an electronic image sensor. In addition, it is possible to provide a focusing method for a high-performance large-aperture wide-angle zoom lens that is particularly compatible with electronic imaging devices. In addition, a wide-angle, wide-angle, high-angle, wide-angle lens with a wide angle of 75 ° (a focal length of 28 mm in terms of a 35 mm version) suitable for a single-lens reflex camera using a 6-megapixel class small electronic image sensor. A zoom lens can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a lens arrangement at a wide-angle end of a zoom lens according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating a lens arrangement at a wide angle end of a zoom lens according to a second embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a lens arrangement at a wide-angle end of a zoom lens according to a third embodiment of the present invention.
FIG. 4 is a cross-sectional view showing a lens arrangement at a wide angle end of a zoom lens according to a fourth embodiment of the present invention.
5 is an aberration diagram for Example 1 upon focusing on infinity. FIG.
6 is an aberration diagram for Example 2 upon focusing on infinity. FIG.
FIG. 7 is an aberration diagram for Example 3 upon focusing on infinity.
8 is an aberration diagram for Example 4 upon focusing on infinity. FIG.
FIG. 9 is a diagram showing a schematic configuration of an electronic camera to which the zoom lens of the present invention can be applied.
FIG. 10 is a diagram showing a schematic configuration of a video camera to which the zoom lens of the present invention can be applied.
FIG. 11 is a conceptual diagram when a first lens group is used as a focus group in a conventional zoom lens.
FIG. 12 is a conceptual diagram when a negative lens group is arranged on the image side in a conventional type zoom lens and this group is used as a focus group.
FIG. 13 is a conceptual diagram illustrating a configuration of a zoom lens according to the present invention.
[Explanation of symbols]
G1 ... 1st group
G2 ... Second group
G3 ... Third group
G4 ... 4th group
G5 ... 5th group
S ... Aperture
11. Electronic camera
12 ... Objective optical system for photographing
13. Half mirror prism
14 ... Penta prism
15 ... Eyepiece
16 ... Release button
17 ... Strobe
18 ... LCD monitor
19 ... CCD
20 ... Controller
21 ... Data writing device
22 ... Low-pass filter
23 ... IR cut filter
24 ... Video camera
25 ... LCD (Liquid Crystal Display)
26 ... ON / OFF switch
27 ... Recording microphone

Claims (1)

In order from the object side, a first group having a negative refractive power, a second group having a positive refractive power, a third group having a negative refractive power, a fourth group having a positive refractive power, and a positive refractive power. Comprising a fifth group having
Zooming from the wide-angle end to the telephoto end is performed by reducing the distance between the first group and the second group and the distance between the third group and the fourth group, and the distance between the second group and the third group, and Increasing the distance between the fourth group and the imaging surface, decreasing the distance between the third group and the fifth group, and increasing the distance between the fifth group and the imaging surface ;
Focusing at the time of moving an object point is performed by the fifth group. In this case, when focusing from a short distance to an infinity direction, the fifth group is moved to the image side, and from the infinity direction to a short distance direction. In the zoom lens, the fifth lens group is moved to the object side to satisfy the following condition .
(1) -0.2 <β _V <0.8
(2) 0.6 <Δ _L5 / Δ _L4 <1.2
(3) 0.05 <D ₄₅ / f ₅ <0.15
However, β _V is the magnification of the fifth group at the time of focusing on the infinite object point at the wide angle end, Δ _L4 is the amount of movement from the wide angle end to the telephoto end in the infinite object point focusing state of the fourth group, and Δ _L5 is A moving amount from the wide-angle end to the telephoto end in the infinite object point focusing state of the fifth group, D ₄₅ is on the optical axis of the fourth group and the fifth group at the time of focusing on the infinite object point at the telephoto end. air space, f ₅ is the focal length of the fifth group.

Images